Shareholders have increased pressure on Tesco to scrap its US ventures and pull out of banking with renewed calls for it to focus on rejuvenating its flagging UK retail business.

At the start of a critical fortnight in which the chief executive, Phil Clarke, is to unveil his blueprint for the supermarket group's future, investors have reportedly spoken out against the "disastrous" transatlantic foray.

A fund manager at Legal & General Investment Management, Tesco's third largest shareholder with a 4% stake, said Tesco "needs to think long and hard about what it wants to be". L&G's Richard Black told the Sunday Times: "Can it be everything to everyone, or should it focus on its gem, the British grocery business? Of course, this is likely to raise questions about other areas of the business, such as America and the bank."

Another institutional investor in Tesco, speaking anonymously, said the US Fresh & Easy stores were a "disaster" and once the level of losses had become obvious, Tesco "should have pulled back faster".

Fresh & Easy has made trading losses of £500m on top of the £800m investment Tesco has made since its launch four years ago. The banking arm, struggling with IT problems, has yet to deliver promised current accounts. The supermarket giant issued its first profits warning for 20 years in January, and shares have fallen 21% over the past year. Tesco's market share is now at its lowest level for almost seven years, at just below 30%, although still some way ahead of its closest competitor, Asda.

Shareholder concerns have been reported in the financial press, with one top investor saying it believes another profits warning could be on the way. January's news was stark enough to prompt the Invesco Perpetual fund, which was Tesco's fifth largest shareholder, to sell its entire stake.

Tesco's annual results will be published next week on 18 April, at the same time as Clarke delivers results of his strategic review. Clarke, who took over from Sir Terry Leahy last year, is reported to be considering changes to sales promotions and to be looking at ways to create "warmer" stores, including deploying more staff to assist customers. Innovations tested at 200 selected stores are to be extended across Tesco's 2,800 UK stores.

Last week Tesco announced it would be altering its Value brands to give a more upmarket look and healthier quality to the cheapest items on its shelves.

Separately, Tesco's stores were criticised by rival Sainsbury's boss Justin King, who said that the main reason retailers struggle is that "they stop doing a great job for customers". He told the Sunday Telegraph that "certain people have executed big shops in a way that customers don't like".

A Tesco spokesman said: "We stay close to our investors and know what they expect from Tesco." He added that they had "a clear target to break even in America".